Sonic Adventure 2 is the sequel to Sonic Adventure. It was released in 2001 on the Sega Dreamcast to mark the tenth anniversary of the first Sonic game, Sonic the Hedgehog. Many billboards and posters promoting the game had Sonic wearing Soap Shoes, and in-game billboards also depicted the shoes.

This game was ported to the Gamecube in 2002 with slightly improved graphics and an improved multiplayer mode under the name Sonic Adventure 2: Battle. Some characters in multiplayer were taken out, and some new ones were added. Also, there were some cameos in the story mode that you can obtain by pressing a certain button. The Chao-raising system was also improved. It now enabled players to check their Chao's stats within the game and transport a Chao to a copy of Sonic Advance, Sonic Advance 2 and Sonic Pinball Party using the Gamecube-Gameboy cable.

The gameplay is split in 3 different gameplay types. As Sonic and Shadow (Speed), the gameplay is similar to the old 2D Sonic games, where you get to the goal as fast as you can. As Tails and Eggman (Shooting), you go through the level at a slower pace and shoot enemies as you go along. As Knuckles and Rouge (Hunting), you search each level using the emerald radar to find pieces of the Master Emerald.

On a top secret military base on a secluded island, Dr. Eggman leads a one-man siege and releases the base's secret - a living superweapon called Shadow. Shadow instructs Eggman to speak to him aboard the Space Colony ARK to discuss plans. As Eggman makes his way back to his base, he decides to make another attempt to steal the Master Emerald from Knuckles. Interrupting Knuckles' fight with a treasure hunter named Rouge, Eggman makes his move. However, Knuckles breaks the Emerald, forcing both himself and Rouge to find the shards. Eggman continues to his base while Shadow takes the city route. Shadow breaks into a bank to steal a Chaos Emerald. He is mistaken for Sonic, who is promptly arrested. Sonic breaks free of custody, but is eventually recaptured after an encounter with Shadow.

Meanwhile, Rouge breaks into Eggman's pyramid, and follows him to the Space Colony. Aboard there, Eggman and Shadow discuss their plans to dominate the world using the Eclipse Cannon. As they finish their discussion, Rouge reveals herself and offers to help. The three of them head back to the island to put their plan into action. Eggman clears out the defences and eventually arrives on an aircraft carrier. There, Amy mistakes Shadow for Sonic, and Eggman takes the opportunity to attack. She is rescued by Tails. While Rouge heads off to steal the Chaos Emeralds, Tails and Amy rescue Sonic. Eggman instructs Shadow to set the timer on the explosives he has planted. Rouge quickly finds the Chaos Emeralds, but this results in her being trapped in the Security Hall. Shadow races through the forest as Sonic escapes through the harbour. They fight until Eggman reminds Shadow of the countdown. While Sonic escapes, Shadow rescues Rouge just before the charges go off. Sonic escapes successfully, while Knuckles continues his shard search in the mountains.

Eggman and Shadow test fire the Eclipse Cannon on the planet's moon. They then debate how to get the sixth Chaos Emerald. Rouge arrives with a newspaper saying Tails has it after the Station Square incidents. Tails, meanwhile, helps Sonic and Amy to escape from being captured again. Knuckles soon arrives from the sewers and joins their team. While Tails chases the President to save him from Eggman, Rouge chases Tails for the Emerald. He escapes from her, and Shadow takes up chasing through the mountains Knuckles visited earlier. Tails, Sonic, Amy and Knuckles reach Eggman's pyramid and successfully infiltrate it. They use Eggman's spacecraft to reach the Space Colony. As they approach it, Knuckles and Sonic fight for the controls, causing it to crash. While Knuckles searches for the remaining shards, Tails begins his plan to use a fake Emerald. Sonic is told by Eggman that he has captured Amy, and Sonic sets off. Outside, Knuckles battles Rouge for the shards, a battle which nearly kills Rouge. Surviving only because Knuckles saved her, Rouge surrenders the shards.

As Knuckles and Rouge return to the Colony's interiors, Sonic arrives in Eggman's control room. Eggman, apparently aware of the fake Emerald ploy, tricks Sonic into walking into a capsule. Sonic says his goodbyes to Tails and Amy and is ejected from the Colony. The capsule explodes in space and Amy breaks down. Tails angrily attacks Eggman. Elsewhere aboard the Colony, the Chaos Emeralds are assembled by Rouge. Wanting to use the effects of the Emeralds herself, she was interrupted by Shadow. He has to leave when Eggman informed him that something was heading for the Eclipse Cannon. This turns out to be Sonic, having escaped using Shadow's Chaos Control. Sonic and Shadow fought on the way to the Eclipse Cannon. As Eggman attempts to fire the weapon, it fails due to Sonic attacking it.

All seven inhabitants of the Colony return to the control room. A recording comes through from Eggman's grandfather, Prof. Gerald Robotnik. He announces his plan to destroy the planet using the Colony to do it. Tails, Eggman, Knuckles, Rouge and Sonic set off to stop the Cannon. Amy eventually persuades Shadow to join them, and he defeats Gerald's dangerous mutant, Biolizard. Knuckles uses the Chaos Emeralds, and the Biolizard disappears. However, it turns out to have merged with the Eclipse Cannon, becoming the Finalhazard. Rouge explains that it is now heading for the planet. Sonic and Shadow use the Chaos Emeralds to become Super Sonic and Super Shadow. They defeat the Finalhazard and use Chaos Control to move the Colony away from the planet.

Boss Rush is unlocked after either the Hero, Dark or Final storylines are completed and is essentially all the games bosses for the respective storyline played in a row in a survival mode. The player is given 5 lives at the start.

The Kart Racing mode can be played with one or two players and is a typical racing game featuring the 6 playable characters from the game. Downloadable extra tracks and themes used to be available for the Dreamcast edition.